Method and tool for producing face clutches



Nov. 1946. v E. WILDHABER 2,410,913

METHOD AND TOOL FOR PRODUCING FACE CLUTCHES fild igy '8, 1942 s Sheets-Sheet 1 Nov. 12, 1946. p E. WILDHABERO 2,410,913.

IIETHOD AND TOOL FOR PRODUCING FACE CLUTCHES Filed lay a, 1942 a Sheets-Sheet 2 O Snberitot ERNEST wan/maze (Ittomgg Nov. 12, 1946. E. WILDHABER I 2,410,913

METHOD .AND TOOL FOR monucme FACE CLUTCH'ES f I Filed May a, 1942; 8 Sheets-Sheet 3 5 I ,7 Q 1 g I v, v

15 8! Emvssr wu. 014055 Nov. 12,1946. E. WILDHABER 2,410,913

IIETHOD AND TOOL FOR PRODUCING FACE CLUTCHES Filed lay a. 1942 a Sheets-Sheet 4 22 [9f I 3npntor ERNEST wan/mask attorney Nov. 12, 1946. E. WILDHABER 2,410,913'

METHOD AND TOOL FOR PRODUCING FACE CLUTCHES Filed May 8, 1942 8 Sheets-Sheet 5 3nuentor ERNES 7' WILD/m 55/:

Nov. 12, 1946 E. WILDHABER 2,410,913 METHQD AND TOOL FOR PRODUCING FACE CLUTCHES Filed May 8, 1942 8 Sheets-Sheet 6 V za- 240' 245' 254 e/vesr WILD/{885R Nov. '12, 1946. E. WILDHABER METHOD AND TOOL FOR PRODUCING FACE CLUTCHES Filed May 8, 1942 8 Sheets-Sheet '7 337 540 334' I 33 my 4}? Summer ERNEST W/LDHfiBEK Nov. 12, 1946. E. WILDHABER I I METHOD AND TOOL FOR'PRODUCING 'FACE GLUTCHES Filed Maya, 1942 '8 Sheets-Sheet a Patented Nov. 12, 1946 METHOD AND TOOL FOR PRODUCING FACE CLUTCHES Ernest Wiidhaber, Brighton, N. Y., assignor to Gleason Works, Rochester, N. Y., a corporation of New York Application May 8, 1942, Serial No. 442,210

31 Claims. (c1. 90-9) The present invention relates to face clutches and particularly to those having longitudinally straight teeth, and to methods and tools for producing face clutches.

Face clutches may be classified or divided into four different types, namely, fixed face clutches or couplings, where the two clutch members are rigidly bolted together, axially adjustable face clutches, whose members stay in enga ment but are not rigidly held together, releasable face clutches, which are repeatedly engaged and disengaged, and load-releasing face clutches, which are constructed to automatically disengage under excessive loads. I

Face clutches can'be made with either straight or longitudinally curved teeth. The processes heretofore employed for cutting straight-toothed face clutches have been relatively slow. Face clutch members having longitudinally curved teeth of zero spiral angle can be out quite rapidly, however. If it is desired to out both sides of a -tooth space of such] a clutch member simultaneously, though, it is necessary to adapt the structure of the clutch to the process of cutting. For instance, the taper in depth of the tooth spaces has to be increased, so that the tooth spaces are cut deeper at their outer ends. Particularly is this true of fixed face clutches with longitudinally curved teeth. This is, of course, a

disadvantage. Y

One object of the present invention is to provide a process for cutting the tooth spaces of straight-toothed face clutch members which will be substantially as fast as the methods employed for cutting curved-tooth face clutch members.

A further object of the'invention is to provide a process for cutting straight-toothed faceclutch members which will permit cutting two sides of a tooth space of such clutch members simultaneously without requiring. any increase in depthwise taper of the tooth spaces.

A further object of the inventionisto provide a cutter for and method of cutting straighttoothed face clutch members which will permit of successively roughing and finishing both sides of a tooth space of such clutch members in a single revolution of a cutter.

Releasable face-clutch members ordinarily have the tops of their teeth chamfered to facilitate engagement and disengagement. Another object of this invention is to provide a cutter for and method of cutting releasable face clutch members with proper chamfer at the tops of their teeth.

Still another object of the invention is to pro- 55 lead.

vide a cutter for and method of cutting toothed face clutch members whereby one side of a tooth space may be cut and the opposite side ehamfered' in a single revolution of the cutter.

A still further object of the invention is to pro- 'vide face clutch members whose teeth are properly chamfered at their tops, so that even when the chamfered portions of the teeth only are in engagement, contact will be made in the middle of the length of theteeth and not be concentrated at the tooth ends.

Other-objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In cutting face clutches according to the present invention, a cutter is employed that is of the disc type. Preferably the cutter has cutting blades arranged part way onlyaround its periphery with one or more gaps between blades. Preferably the cutter is provided with both roughing and finishing blades. ,A tooth space of the work may be roughed out during depthwise feed of the cutter into the work, and the tooth space may be finished simply by rotating the cutter in engagement with the work after full depth is reached. Alternatively, theroughing operation may be effected during a combined lengthwise and depthwise feed of the cutter in one direction and finishing accomplished during a return lengthwise feed in the opposite direction, after the cutter has reached full depth position,

Where the cutter employed has its blades arranged in two or more groups with a gap between the last and first blades of each group, each group may consist of both roughing and finishing blades. Rough-cutting and finish-cutting of one side of a tooth space may be accomplished with one group of blades during depthwise feed of this type of cutter into the blank. Then the cutter may be withdrawn from engagement with the blank, and the blank indexed half a pitch to bring the opposite side of the toothspace into cutting position. Then the cutter may again be fed into the blankto rough and finish-cut this latter side of the tooth space with the second group of blades, and then the cutter may again be withdrawn from engagement with the blank and the blank may be indexed again hrough half a pitch to bring one side of a new tooth space of the blank into cutting position.

One feature of the present invention is the provision of novel types of releasable and loadreleasing clutches having teeth whose chamfered top portions are helicoidal surfaces of varying with. this construction, the inclination of the chamfered portions of the teeth with reference to the clutch axis changes from the inner to the outer ends of the clutch teeth and the clutches will have proper contact even when sliding into or out of engagement.

Like the sides of the teeth, the chamfered portions may be cut with a cutter having cutting blades arranged part way only around. its periphery. The chamfer may be cut simultaneously with the cutting of the sides of the clutch teeth by employing a cutter whose blades are so shaped as to cut one side of a tooth space and chamfer the top of the opposite side of the tooth space simultaneously. Such a cutter may have its blades arranged in two groups; one group may cut one side and chamfer the opposite side of a tooth space and the second group may cut and chamfer, respectively, the sides of the tooth space opposite to those operated on by the first group of blades. The work may be indexed through half a pitch between operationsof the two groups of cutting blades so that the whole of the tooth space may be cut and chamfered in a single revolution of the cutter.

It is preferred to make fixed face clutches with opposite side tooth surfaces which are inclined to the clutch axis and converge in the clutch axis, but both axially adjustable and releasable face clutches are preferably made with side tooth surfaces that extend in the direction of the clutch axis. For cutting the first named type of clutch, the cutter is provided with finishing blades which are inclined to the cutter axis at other than right angles. For cutting the two last named types of clutches, the cutter is provided with blades whose sides are perpendicular to the cutter axis. Clutches of the load-releasing type are preferably provided with helical side tooth surfaces of constant lead. Such clutches may be cut with cutters having blades of convex profile.

The invention is capable of various other modifull lengthwise tooth v bers made according to this invention in engagefications and embodiments as will be described hereinafter.

In the drawings:

Fig. 1'is an elevational view showing in engagement two members of a fixed face clutch made according to this invention;

Fig. 2 is a sectional view of one of the clutch members, the section being taken in a mean plane, hereinafter referred to as the pitch plane, which is perpendicular to the clutch axis and in which the thickness of the teeth of the clutch member equals the width of its tooth spaces;

Fig. 3 is a fragmentary elevational view on an enlarged scale of one of the clutch membersr Fig. 4 is a fragmentary sectional view of a pair of the clutch members in engagement, the section being taken on a line corresponding to the line 44 of Fig. 5;

Fig. 5 is a diagrammatic view, showing one of the clutch members fragmentarily in axial section. and illustrating diagrammatically one method of cutting such a clutch member;

Fig. 6 is a. plan view of one form of cutter for cutting face clutches of the type disclosed in Figs. 1 to 5 inclusive;

Fig. 7 is a diagrammatic view illustrating the shape of the finishing blades of this cutter;

Fig. 8 is a diagrammatic view, illustrating the shape of the roughing blades of this cutter;

Fig. 9 is a fragmentary sectional view taken in the pitch plane of a clutch of modified form which has teeth so shaped longitudinally that contacting tooth surfaces of the two clutch memment;

Fig. 13 is a fragmentary axial sectional view of one of the clutch members and illustrating diagrammatically one method of cutting the same;

Fig. 14 is a fragmentary elevational view further illustrating the preferred method of cutting this clutch member and showing in operation one blade of a cutter, such as may be employed for cutting this clutch member;

' Fig. 15 is a plan view and Fig. 16 an axial sectional view of a preferred form of cutter for cutting this type of clutch member;

Fig. 17 is a developed sectional view of this cutter;

Fig. 18 is a fragmentary view showing a pair of releasable clutch members made according to,

this invention about to be engaged with one an: other;

Fig. 19 is a corresponding view showing the releasable clutch member made according, to this invention;

Fig. 23 is a fragmentary diagrammatic view illustrating how the chamfer on the teeth of an adjustable clutch member might be produced according to the present invention:

Fig. 24 is a diagrammatic view illustrating one method of cutting ,the sides of the teeth of a releasable clutch member according to the present invention; a

Fig. 25 is a diagrammatic view illustratingthe timed relation between the rotation of the cutter and the lengthwise feed of the cutter across the face of the blank in the method of Fig. 24;

Fig. 26 is a fragmentary view showing a blade of a cutter made according to one embodiment of this invention for cutting the side surfaces of the teeth of a releasable clutch member, and illustrating the side-cutting operation;

Fig. 274s a corresponding view showing ablade of a cutter for chami'ering the teeth of such a clutch member, and illustrating the chamfering operation;

Fig. 28 is a corresponding'view showing a blade clutch member of this type taken in a plane'pe'rpendicular to the clutch axis;

Fig. 31' is a fragmentary elevational view of such a clutch member;

Fig. .32 isa, diagrammatic view showing howthe theoretically requlredproflle shape of such a clutch member'may be approximated-by a circular arc; I

Fig. 33 is a fragmentary elevational view illustinting diagrammatically the action of a. load-j releasing clutch constructed according to the pres ent invention;

Fig. as loan elevational view ore-releasable clutch constructed according to this invention;

Bots-a section in a plane perpendicular to the clutch. axisand Fig. 36 isa section in an axial plane oi a load-releasing-clutch member con-'- structeds cording to a still further embodiment of 7 this invention;

is a diagrammatic view, illustrating one method of cutting this clutch member;

Figs. and 39 are views corresponding to Figs.

35 and 35, respectively, and illustrating a'further method of cutting load-releasing clutch members according to this invention;

Figs. so, ii and 42 are diagrammatic views further illustrating the method of'cuttlng load-releasing face clutches according to this invention and showing, respectively, the shapes of the cutter blades'which cut at the large end, center, and small and of th tooth. spaces of the clutch in this method;

Figs. a3, 4.4 and as are corresponding views,

showing the shapes of-the blades of a modified form of cutter;

Fig. {it is a sectional view in aplane perpenv dicular to the axis and Fig. 4? 1s a fragmentary sectional view in an axial plane of one member of a lced-peleasing type clutch constructed ac.-

cording to a further modification or this invention;

Fig. i8

a sectionalview'in aplane perpenits-periphery with "a gap 82' between the last and first segments. Each the segments has a plurality of cutting blades or teeth; in-the embodimentshown, four;

1 Preferably the cutter isprovided with both roughing 'and'finishing bladesp The roughing tloncf'cutter rotation. v

a The :roughlng blades maybe 0! the type shown dicular to the axis of the mating load-releasing clutch member;

Figs. is, to and iii are views'of the blades,

which are adapted to operate at the outer end,"

center, and inner end oi a tooth space, respcc tively, in a cutter ccnstructedto cuts. clutch member such as shown. in Fig. 46; and

Figs. 53 and 5dare corresponding views of the blades of a cutter suitable for cutting the mating member of clutch.

fieierence will be had first to the fixed face clutch whose structure is illustrated-in Figs. 1 to 5 inclusive. "the two members Bil and Bi of this clutch. are preferably made identical with one another, and in the interest of brevity, therefore,

the structure of oniycne member, the member as, will be described in detail. It has straight radial teeth 52 and tooth. spaces 63. Its teeth 62. and

tocthspaces $3 taper in width and height from their enter to their inner ends." The opposite sides be and fit of its teeth are planes which converge towards the tops of the teeth and intersect in the clutch axis 66. Said plane's; therefore, in-- tersect the pitch plane M of the clutch member,

which is the sectional plane of Fig. 2, in'radial' straight lines 68 and to which intersect in the clutcl'i axis $6. The planes oi opposite sides of a I tooth space, moreover, it extended, intersect in a straight line to (Figs. 3 and 5) which lies in the" central plane of said tooth space and intersects the axis of the clutch memberin the pitch apex ll of the clutch member. The normal 13 at mean point it in a side More. toothof the bladesprecede the finishing blades'in the direcin Fig. 8. Here a roughing blade, such as might be employed for cutting at the top of axtooth space of. the clutch member; is shown in full lines at 83, and aroughlng blade, such as' would oper ate somewhat deeper in the tooth space toward the bottom'thereof, is shown in dotted lines at 83'. The point-widths of successive roughing blades ivary. therefore," in accordance with the" position in the tooth space at which the blade is to cut. All the roughing blades have wide topcutting edges 86 and straight parallel sides 86 and 81, that are perpendicular to the axis 88 of thecutter, and the sides .86 and; 8'! of these blades are beveled .ofi nearwthelr tops where they join the top-cuttingedges B5.

The finishing blades of the cutter. may be of i the type shownin Fig.- '7, having opposite side edges 88 and which-converge to their tip so that the blades are of general V shape, Thepoint-widths of the finishing blades, like the point-widths of the roughingblades, vary. The

finishing blade 91, which is adapted to cut at the outer ends of the tooth spaces of the clutch member, is shown in full lines in Fig. land a flnishing blade, which is intended to out further along the tooth space nearer tothe clutch axis, is shown is dotted lines at 9|. l

Preferably the roughlng 'andflnishing blades are made all, of the same height so that the tipcutting edges of these blades lie-in the same -cy lindrical surface (Fig. 6) concentric of the cutter axis 98. Preferably, also, the gashes 84 between. successive blades of the cutter are made of uniform depth 50 that the bottoms 87 of these sashes will all liein'the same cylindrical surface t8 concentric of the cutter axis 96.

All blades are relieved on their tips back of their tlpcutting edges. In addition, the finish-,,

lng blades are relieved on their sides back of their side-cutting edges.

In the preferred operation, the cut in the tooth V space 01 aclutch member el starts with the axis of the cutter at position 96' (Fig. 5). As the cutter rotates on its axis, it is fed longitudinally of the tooth space and also depthwise into the tooth space so that the axis of the cutter travels along the inclined line 99 (Fig. 5). During thls lengthwise and depthwise feed movement, theroughing 7 blades of the rotating cutter come successively into operation and rough out the tooth space.

When the cutter has been fed beyond the full length of the tooth space, its direction of length wise feed is reversed. The cutter itself, however,

continues to rotate on in the same direction. The

depthwise feed movement continues, moreover, until the cutter reaches full depth positlonwith its axis at 8611., Thenthe depthwiseleed movementls' discontinued. 'It is preferred, as illusdo all trated, to have the reversal of the lengthwise.

space of the clutch member and its axis has reached position 96", During this reverse lengthwise feed movement, the finishing blades of the cutter operate and finish-cut the sides of the tooth space. When the finishing cut is completed, the cutter is quickly withdrawn in a depthwise direction, as indicated by the dotted line 9I"'96 and returned to initial position with its axis at 96. Thewithdrawal movement occurs while the gap 82 in the'cutter is abreast of the blank, and the blank is indexed during the withdrawal movement.

Thus in a revolution of the cutter, a tooth space of the clutch member will be roughed out and finished. The roughing blades of the cutter are wide enough to reach across the full width of the tooth space and leave on Just enough stock for the finishing blades to remove inthe finishing cut. Hence. the full width of a tooth space is cut at all times, even during the depth feed of the cutter, The roughing blades cut principally with their top cutting edges 85, while the finishing blades cut principally with their side edges 88 and ill. Both the roughing and finish cutting operations are, therefore, very efficient. v

The combined rotary motion and feed of the cutter can be considered as a rolling motion whose instantaneous axis is, for instance, at I" when the axis of the cutter is at position 96" intermediate the'ends of the finishing feed movement. The mean point I4 in the side surface 84 of a tooth is finished when the normal 13 to the side surface of the tooth at this point passes through the instantaneous axis I00.

95' (Fig. denotes the position of the tip cutting surface of the cutter at the beginning of the cutting operation when the axis of the cutter is at 96'. 95" denotes the position of the tip cutting surface of the cutter when the cutter is in full depth and its axis is at N" in the middle of the return finishing feed movement.

It will be understood, of course, that instead of imparting the lengthwise and depthwise feed movements to the cutter, either or both of these motions may be imparted to the work instead, and the cutter simply rotated on its axis. I

Preferably fixed face clutches are made so that the contacting teeth will have less than full length engagement or bearing. In this way the ends of the teeth are relieved of pressure. Thus, as illustrated in Fig. 9, each clutch member may be provided with teeth whose sides are longitudinally convex so that the mating tooth sides will engage with localized contact or bearing. Here IIII denotes teeth of one clutch member and III denotes the teeth of the other. The axis of the clutch is at II2. Opposite sides of the teeth of both members are longitudinally convex, as shown, so that mating tooth surfaces have a contact which is heaviest at their longitudinal centers and which fades away toward both ends ofthe teeth,

Such clutch members can readily be produced by gradually increasing, over standard proportions, the point-widths of the roughing blades from the bladewhich cuts at the center of the tooth length to the blades which cut at the two ends of the tooth space and by gradually widen- 8 ing the point-widths of the finishing blades in a similar manner.

. This construction is illustrated in Fig- 10.

Here the roughing blades of the cutter are de-- noted at-I'I to I26 inclusive and the finishing blades at I21 to I32 inclusive.

Since the tooth space of the clutch member'is widest at its top and has sides which converge to the bottom of the tooth space, and since the roughing operation proceeds with a depthwise as well as a lengthwise feed,and the blade Ill is the first to cut, this blade is the widest of the roughing blades. Ordinarily, the roughing bla'les would then be progressively narrowed in pointwidth to the final roughing blade I 26 which is intended to cut at full depth at the outer end of a tooth space. The finishing blades cut at full depth, and ordinarily the finishing blade I21, which cuts at the large end of a tooth space, would be the widest of the finishing blades, the finishing blade I32, which cuts at the small end of the tooth spaces, would be the narrowest of the finishing blades; and the point-width of the finishing blades would progressively decrease from the blade I21 to the blade I32.

To produce the longitudinally crowned tooth shape, the point-widths of the blades, which cut at the two ends of the tooth spaces, are increased over standard dimensions, that is, the opposite side edges of the blades are gradually onset from their conventional positions beginning with the blade which is intended to cut midway the length of a tooth space. This ofl'set increases progressively from this middle blade toward the blades which cut at both ends of the tooth space. As a result, theopposite side edges of the roughing blades in the view of Fig. 10 lie in curved lines I33 and I34 and the opposite side-cutting edges of the finishing blades II! to I32 lie in curved lines I35 and I38.

Fig. 11 shows a modified form of fixed face clutch in which each clutch member I has teeth III of constant depth from end to end. The sides of the teeth of this clutch member will, however, otherwise be of the same shape as the clutch previously described. If the clutch mem- -bers are to engage with full length contact, then, the sides of the teeth Ill will be plane and will converge in the clutch axis I12. If the clutch member I" is to have localized tooth bearing, then these teeth will be of the shape shown in Fig. 9.

The same cutting cycle, as previously described, may be employed in the production of the clutch member I40; the only difference is that the finishing feed stroke will be parallel to the pitch plane I43 of the clutch member rather than inclined thereto as in the instance of the clutch members illustrated in Figs. 1 to 5 inclusive and 9.

The principles of the present invention are not limited to the production of fixed face clutches but, as shown in Figs. 12 to 17 inclusive. may also be applied to face clutches of the axially adjusts able type. Here again the tooth sides of the clutches are planes which converge at the clutch axisin the same way as the clutch of Fig. 2. In the embodiment illustrated, however, the sides of the teeth of the axially adjustable clutch extend in the direction of the clutch axis instead of being inclined thereto as is the case with the fixed clutch of Figs. 1 to 5. I

A pair of engaging axially adjustable clutch members are shown at I 50 and III in Fig. 12. The teeth of each clutch member have sides In which are, as stated. plane and parallel to the clutch axis I54. Preferably the top surfaces I55 of the teeth are also plane and are perpendicular to the clutch axis I54. I

Preferably the two sides of a tooth space of each clutch member are cut successively in a single revolution of a rotary disc cutter. A cutter suitable for this purpose is'shown at I60 in Figs. 15 to 17 inclusive. This cutter has its cutting blades arranged in two groups, one group being, intended to rough-cut and finish successively one side of a tooth space and the other group being intended to rough-cut and finish successively the opposite side of thetooth space. I

The cutter may again be of the segmental type. The cutting segments for cutting one .side of a tooth space are denoted at I6I and the cutting segments for cutting the opposite side ofa tooth space are denoted at I62. In the'form shown, each segment comprises four cutting blades or teeth, and the two groups of segments are separated byperipheral gaps I63 and I66.

In the preferred construction, the final cutting tooth or blade of each group is a finishing blade and all of the preceding blades of the group are roughing blades. The finishing blades of the two groups are denoted at I65 and I66, respectively, (Figs. 15 and 1'1), while the roughing blades of one group are denoted at I61 and of the other group at I68. I v

The opposite sides I12 and I13 of eachblade are parallel and perpendicular to the axis I1I of the cutter. 'The tip edges I14 of all of the blades are preferably disposed at the same radial distance from the axis "I of the cutter so as to lie in a cylindrical surface I16 concentric with the axis of the cutter. The twogroups of blades are disposed, respectively, at opposite sides of a plane I10, hereinafter-called the, cutter plane, that is perpendicular to the axis I1I of the cut-' ter. The roughing blades are intended to cut primarily with their tip cutting edges. The finishing blades I65 and I66, respectively, of the two groups have side-cuttingedges, and these edges are offset laterally with reference to the corresponding side edges of the preceding roughing blades of that group. I g

Preferably the finishing blades are so. arranged that their opposite side-cutting edges I82 and I83, respectively, coincide with the perpendicular to the'cutter axis I1I. Thus thev roughing edges of the two groups are offset at opposite sides of the plane I while the finish: ing edges of blades I65 and I66preferably lie in that plane.

In cutting a face clutch with the cutter I60,

the cutter is so positioned relative to the 'work that the cutter plane I10 passes through and contains the clutch axis I54. One side surface I53 of a tooth space of the clutch is then roughed out by feeding the rotating cutter depthwise intothe work until the cutter reaches full depth position. ,Inthis feed movement, thecutter axis will move from the position I1 I (Figs. 13 and 14) to the position I1 I and the outside cutting 'surface of the cutter will move from position I to position I15". In this depthwise feed movement, the roughing blades I61 of one group of blades of the cutter will cut with their tip cutting edges only, and a slight amount of stock will be left on the side of the tooth space to be removed by the finishing blade.

Fig. 14 is a view showing the cutter at full depth position. After full depth position has been reached, the depthwise feed movement stops, andthe finishing out along 35 ishing blades.

plane- I10 length of the tooth surface is taken by the finishing blade or blades I65. I

The cutter is then withdrawn to starting position. During this withdrawal movement the gap I63 in the cutter comes. abreast of the work and the work is indexed half'a pitch. In this way the opposite side I52 of the tooth space is moved into the cutter plane I10. The depthwise feed then 1 starts anew and proceeds in the same manner as 10 before so that the roughing blades I68of the group I62' rough out the opposite side of the tooth space. After full depth position has been reached,'the feed'again stops and the finishin blade I66 finishes thatside of the tooth space. 15 Then the cutter is withdrawn again from engagement with the .work, and the work is again indexed through half a pitch to bring aside I53 of the next "tooth space into position to be cut. Thus the operation proceeds until all of 20 the tooth spaces have been completed.

In the operation as described, then, there are two complete depthwise feed cycles per cutter revolution, and the work is indexed twice per cutter revolution, each time through half a. pitch.

In other words, a clutch having n teeth is indexed through an angle of 360/2n at every half turn of the cutter.

For the purposes of clearer illustration, the

number of rough ng blades shown in the developed view of Fig. 17 isless than that shown,

in theflcutter of Fig; 15. All of the blades'of the cutter I60 are relieved on their sides as well as their tip surfaces back of their front faces to insure good cutting action especially by the fin- The relieved side surfaces are denoted at,l1'1 and I16 (Fig. 17) and the relieved top surfaces at I16 (Fig. 15)

Because of the side relief, the side edges of the blades will be axially displaced each time the 40 blades'are sharpened. Axial adjustment of the two groups, I6I and I62,- of the blades is re.- quired, therefore, after each sharpening of the cutter. The cutter itself can be adjusted bodily to line up the finishing blade I66 of group I62 with the cutting plane I10, and this automatically disposesthe' roughing blades of that group inthe same offsetrelationto" the cutter plane as'when the cutter isnew; The blades of group, I6! can be brought back' into the properjrelation tothe cuttin Plane I10, after sharpening, by thinning up the spacer or shim I19 which is interposed between the inside surfaces of the segments I 6| and'the adjacent side faceof the head of the cutter I60. Alternatively, the segments I6I themselves can be thinned'up'by grinding of! the inside surfaces I00 after each sharpening. The

amount of stock'that has to be removed from the shims or from the segments is quite. small and can be controlled accurately.

with the-cutting method described, the botf toms of the tooth spaces of the clutch members I50 and I5I will be curved, but the curvature of the tooth spacebottomswill be hardly visible and certainly no drawback, whereas the cutting 55 process itself is fast and eflicient. Furthermore,-

the finish and accuracy of the sides of the clutch teeth is of a very high order because the principal amount of stock is removed from the tooth spacesin th'e roughing operation during the depthwise feed, and the finishing blades of the cutter have only tov remove the slight amount of stock left after full depth position is reached.

Hence the shape and position of the finished side surfaces of the clutch teeth are unaffected by any the whole possible inaccuracies in the depthwise movement.

Face clutches, whose teeth have plane sides extending in the direction of the clutch axis and converging in the clutch axis, can be used conveniently as releasable clutches if the tops of the teeth are suitably chamfered to facilitate engagement and disengagement of the clutch members. The chamfer' is required since one or both of the shafts or other parts, to which the clutch members are secured, may be rotating at high speed when the clutch members are being moved into or out of engagement. Since, at the start of their engagement, a sudden and heavy crash load may be exerted on the chamfered ends of the clutch teeth, the chamfer, moreover, should be such as to enable the teeth to bear in their middle or along their whole lengths'even when only the chamfered parts of theteeth are in contact.

Fig. 18 shows a pair of releasable clutch members about to be engaged and Fi 19 shows these same members in fully engaged position. Where the chamfer consists of an ordinary round extending along the sides of the teeth at their tops, as

illustrated clearly in Fig. 21, thechamfered portions of the teeth will bear only at their ends when in contact. In Fig. 21, the teethof one clutch member are denoted at 3; the teeth of the other clutch member at I94. chamfer consists of a round at the tops ofthe teeth, the chamfered surfaces willbe parts of cylindrical surfaces extending lengthwise of the teeth. Planes perpendicular to the clutch axis I95 then intersect the cylindricalchamfer of the opposite sides of the teeth along straight lines I and I 91, respectively, which are parallel to the plane side surfaces I98 and I 89, respectively, of the teeth. Since the plane sides I98 and I9! of the teeth are radial and pass through the clutch axis I95, the lines I96 and ililwlil be parallel to said sides and offset at opposite sides of the clutch axis I95, and will cross one another.

Because of this, when the chamfered portions only of the mating clutch elements are in contact, they will contact at the 'outer ends only of the chamfered portions of their, teeth, as denoted at 200 in Fig. 21, andthe outer ends of the chamfered portions of the teeth will have to carry the whole of the load when the clutch members are being moved into or out of engagement. This means that the chamfered portions ofthe clutch members will not be able to carry heavy loads and, as a consequence, that the clutch members themselves will be unable to stand heavy loads;

I have discovered that engagement at .the middle of the teeth or also engagement along the Where the whole length of the chamfered surfaces of releasable clutch members can be obtained when the chamfered surfaces are made helicoidal surfacesof varying lead. For clutch members having radial teeth, the helicoidal surfaces giving,

full length contact should be such ,,that their generatrices are straight lines, which extend lonturn of the cutter.

Fig. 24 illustrates diagrammatically a preferred gitudinally of the teeth and radially of the clutch axis in any plane through the chamfered surfaces perpendicular to the clutch axis.

In principle, the proposed chamfer may be described or produced by a point 205 (ll'ig. 23) of a tool Ill which reciprocates radially of the clutch axis 201, while a relative helicoidal movementis produced between the cutting'tool and the clutch about the clutch axis. The radial reciprocation of the tool will cause the point of the tool to describe a straight line perpendicular to and intersecting the clutch axis. In the relative helicoidal movement, the work may be turned slowly on its axis and moved in the direction of its axis at a varying rate as compared with its rotary motion as the tool 2" moves across the face of the clutch. This helicoidal movement will cause the clutch to move from the full line position indicated at 208 in Fi 23 to the dotted line position shown at 208', while the cutting tool is being reciprocated radially of the clutch axis.

When the teeth of a clutch member are chamfered in the described fashion, the elements or Beneratrices of the helicoidal chami'ered surfaces in any plane perpendicular to the clutch axis will extend radially of the clutch axis as do the lines III and III in Fig. 20. When the teeth of two clutch members are provided'with such helicoidal chamfers, they bear along their full length even when they are coming into engagement and the contact is still only on the chamfered portions of the teeth. Thus such clutch members can carry much heavier loads at all times than the conventionaltype of clutch.

A portion'of a clutch member, whoseteeth ill have a helicoidal chamfer, is shown on an enlarged scale in Fig. 22. It will be noted that the inclination of the chamfered portion III of the tooth surfaces to'the clutch axis increases with increasing radial distance from the clutch axis. Thus the profile curve 2| 5 of the chamfered surface at the outer end of a clutch tooth has a greater inclination to the tooth side Ill than the profile curve ill at the inner end of the chamfered portionof the tooth. In other words, the profile curve 2l5 ofthe chamfered portion at the outer end of the tooth has a smaller radius than the profile curve 2H of the inside of the tooth.

In the embodiment shown in Fig. 22, the chamfered portions of the teeth join the side surfaces of the teeth smoothly without break. Thejuncis preferably keptas small as possible.

To produce the desired chamfered surfaces, the

cutting tool maybe fed either depthwise or longitudinally across the face of the clutch blank.

The plane sides of the teeth may be cut by a simple depthwise feed of a tool according to the process described withreference to Figs. 13 and 14. If tooth spaces having straight bottoms are desired, though, a lengthwise feed movement must be produced between cutter and work.

Whether in the cutting of the sides of the teeth pure depthwise feed is employed or a lengthwise feed,'it ispreferred to employ a cutter of the type shown in Figs. 15 to 1'7 inclusive, that is, a cutter having two separate groups of blades for cutting, respectively and successively, opposite sides of the teeth. The two plane sides 216 and M8 of a tooth space are then' cut, as before, in succession, and the work is indexed half a pitch after each half method or cutting the sides of the tooth spaces in such way as to produce tooth spaces with straight bottoms. The cut may start with the axis of the cutter at "in. As the cutter rotates on its axis, it is first fed both in the direction of depth and in the direction of the length of the tooth space until the cutter reaches full depth position with its axis at I'Hb. During this movement, the cutter will have rotated about itsaxis throng an angle 2ZIa-i1l-2Zlb. After reaching f depth position, the cutter is moved in the direction of the pitch surface 222 of the clutch member until its axis reaches position IHc. During this movement, the cutter will have rotated about its axis through an angle equal to 13 22Ib -l1|-22lc. Then the cutter is withdrawn chamfering the opposite side of the tooth-space. fromengagement with the clutch until its axis The cutter may again be of-the general type reaches the position llld; moving along the illustrated in Figs. 15 to 1'1 inclusive, having two dotted line Hie-Hid and'through an angle separate groups of cutting blades separated by 22|c--l'Ii--22ld. During this withdrawal, the 5 peripheral gaps. The blades of the first group gap I68 in the cutter will be abreast of the work may be shaped as shown in Fig. 28 to cut the sides and the work will be indexed through half a pitch. 2|6 of the clutch teeth and chamfer the opposite The cut is then started on the other side of the sides MS of the teeth. The blades of the second tooth space, the cutter being fed depthwise and group of blades of the cutter will then be shaped lengthwise along the full'lirie 224 until the cutter to cut the sides 2" of the clutch teeth and axis again reaches the position File, with the chamfer the sides 2l6 thereof.

cutter at full depth position. Then the cutter is The cutting and chamfering of the clutch teeth fed along the full length of the tooth space withmay beeffected with or without lengthwise feed out depth feed until its axis again reaches posiof the cutter, preferably without lengthwise feed. tion illb. The two sides of thetooth space will 5 In this case, the proc u y be simller to then have been completed and the cutter is again that described with reference to the process illuswithdrawn from engagement with the work so trated in Figs. 13 and ld except that the cutter that its axis will travel alongthe dotted line 225 will be so disposed that its axis will be at a Br -tel until it returns to initial position "1a. In this distance from the clutch axis than is shown in withdrawal, the work is again indexed through Fig. 13. This results in cutting tooth spaces havhalf a pitch. This completes the cycle and'the ing somewhat inclined tooth bottoms. In this cycle begins anew to cut a new toothspace ofthe manner, the chamfered surfaces can becorrectly work, formed. Theplane side surfaces of the clutch During the feed from position 11 Id to lllc, the teeth may also be f y formed in hi 'rmsicutter will rotate through the angl v tion because plane side surfaces areperpendicular 22' e to the cutter axisand independent of the location of the cutter axis radially of the clutch.

while during the reverse travelat full depth po- With the type of cutter illustrated in Fig. 28, sition, the cutter will rotate through the angle therefore, a very efficient method of producing i 22le--l|l--22If, and during the final withdrawal, o a releasable face clutch member is provided,

the cutter will rotate through an angle whereby both sides of a tooth space can be cut I a and chamfered in a single revolution of the cut- The dotted line 221 denotes the position of the Releasable face clutches of' the type described t p cutting ur a of the c tt en the a s ofare superior to the. clash-type clutches conventhe cutter is at H lb. tionally employed, where one clutch member has As already stated, the chamfer may be applied external teeth and the mating clutch member to the teeth in an operation separate from the phas internal teeth. clutch members constructed eration of cutting the tooth sides. Both i so according to the present invention may be made a tooth space may be channeled simultaneously 4 quite rapidly and both members may be cut alike with a rotary c tt g tO l having blades 230 (Fig. and in identical cutting operations. Moreover, 2'!) whose opposite si e edges 232 d ar of the chamfer can be produced on the teeth simulconcave curved profile, preferably circular arcstaneousiy with the cutting thereof, whereas with Successive blades of this cutter may have th i the conventional external and internal type of correspondingside cutting edges differently inclutch, the 'engaging ends of'the teeth have to ciined to a plane 23i perpendicular to the axis of be chamfered in aseparate operation from the the cutter so as to produce a close approximation tooth cutting operation. Further than this, for of the desired helicoidal chamfer surface. Thus, clutches for use in the aeroplane field, the re the centers of curvature of the. corresponding leasable face clutch of the present invention has sides of successiveblades of the cutter may be disthe advantage of reduced weight as compared placed axially and radially of the cutter in a diwith an external-intemal typeof clutch. rection inclined to the plane 23! in accordance Figs. 29 to 32 inclusive demonstrate how the with the inclination of a tangent to the helicoidal desired helicoidal surface of varying lead may be surface at a mean point in the tooth length. The approximated by a surface of revolution and line 234 (Fig. 2'?) denotes the line of centers of theseflgures hence show how arotary cutter, such different cutting edges at one side of the cutter, 'as'described just above, may be usedto"produce and 235, 236 and 231, denote, respectively,'the thedesired type of chamfer on'the clutch teeth centers of the blade profiles for the blades which in a. depthwise feed operation. These figures also cut at the outer end, a mean point, and the inner demonstrate how a load-releasing type of clutch end of a tooth space, respectively. The cutter 50 can be cut with side tooth surfaces that are surmay have its blades arranged part way only faces of revolution but which approximate around its periphery with a gap between the last helicoidal surfaces of varying lead to accomplish and the first blades for indexing. It can be fed the purposes of the present invention. In fact, across the face of the blank in one direction to it is specifically with reference to the latter type chamfer both sides of a tooth space, and may be c5 of clutch that these figures deal. "These figures returned to initial position while the indexingis demonstrate that a varying lead helicoidal side being eifected. surface of a' tooth. can be approximated by a Instead of producing the chamfer in'a separate surface of revolution, and it is obvious therefore operation from the side-cutting operation, one that they demonstrate also that a chamfered side of a tooth space may be cut and the opposite helicoidal portion ofv varying lead can also be side chamfered simultaneously. Here a cutter approximated by a surface of revolution. will be employed that has cutting blades such as Let us consider a mean point 245 (Fig.30) in shownat 240 (Fig. 28). The blade 240 has a the length of a side surface 246 of a clutch memstraight side 24! for cutting one side of the tooth her 248 whose side surfaces 248 are radialof the space and a curved side cutting edge 242 for v5 clutch axis 250. 'The tangent to a helix 'at point pitch cone apex 2" of the outer ends of the tooth 24! appears as a line 2 perpendicular to'the radial line252 and intersecting the plane 253 central of the tooth space in a point 2. The inclination of this tangent to the drawing plane of Fig. 30 is given or known from the given instantaneous lead of the helicoidal surface. It equals the lead angle of the helicoidal surface at point 245. We can therefore determine the position of the point 254 axially of the clutch, and locate point 254 in Fig. 29. This point and the clutch are points in the plane tangent to the helicoidal surface at point 2, and their connecting line 255-2" (Fig. 29) is the line of intersection of said tangential plane with the central plane 253, which is the plane of the drawing of Fig. 29. A normal to the helicoidal surface at point 2 appears, therefore, as a line 250, perpendicular to the line 255-254 in Fig. 29.

By projecting point 2" to the line 255-2", point 245' is obtained. Then a line 2" is drawn through the point 245' perpendicular to the clutch axis 259. If we repeat the procedure given for mean point 2" at other at the ends. respectively, of the tooth surface, which all have the same axial position, we find that points 260' and 2M, which correspond to point 245', all have the same axial position and that these latter points all lie on the line 2". This enables us quickly to draw the tooth normal at any point in the line 252, such as at the point 269.

To determine point 269' on line 259, draw line 260-290 parallel to the clutch axis 2", and draw a normal 262 through point 269 perpendicular to the line 255-289. If the normals 2", 262, and 264 at the points 245, 2" and 2", respectively, are determined as above, or individually, asdescribed for the point 245, we find that in the view of Fig. 29 they intersect'substantially in a point 265. More exactly, they envelop a curve whose mean point is at 265. In any case, the desired shape of the surface area along the line 252 can be closely approximated by a surface of revolution whose axis is at 2" and is perpendicular to the plane of the drawing of Fig. '29, and whose normals seemingly intersect at 2". This surface can be described or swept over by rotating the straight line 252 about the axis 2". Its nature is well known. It is a hyperboloid of revolution whose profile in an axial section is a hyper-bola 2. (Fig. 32). It may be approximatedin the region used by a circle 20'! whose.

center is at 208. 7

To obtain the localized bearing and relief at the ends of the teeth, the radius of this circle may be made omewhat smaller than the curvature radius of the hyperbola at its mean point.

The different inclinations of the profile tangents at different points along the lengthof thetooth surface are clearly shown in Fig. 31 which shows fragmentarily a load-releasing clutch member made according to this invention. 210 and 2?, respectively, denote the tangents to a tooth surfaee'2l2 of this clutch member at the inner and surface, respectively.

In the cutting of a tooth space of the clutch member 248, the rotating cutter is preferably fed depthwise into the work until the cutter axis reaches position 265 where the feed movement stops. 'The final shape of the tooth sides is produced in this position by the finishing blade or blades of the cutter. The depthwise feed motion may be in the direction of the clutch axis 289.

The clutch, whose members have helieoidal side points 260 and 2H tooth surfaces of varying lead as described, may

be used as a load releasing clutch. The action of such a clutch is shown in Fig. 33. The two members of the clutch are shown in full lines at 2 5 and 215 in completely engaged position. A further position of the clutch member 21! when nearly disengaged is shown in dotted lines at On this type of clutch, the pressure angle or inclination of the tooth profiles increases in the direction of tooth height. At the tops of the teeth, namely, in the dotted line position shown at 215, the higher pressure angle portions of the tooth surfaces are in engagement with the result that the separating force is transmitted torque. This is often desirable where the clutch is to be thrown out of engagement when an excessive load comes on.

If the profiles of the clutch become more curved than is desirable, as is likely when the number of teeth in the clutch members is large, then the two sides a tooth space of the clutch are then cut successively by the method illustrated in Figs. 13 and 14 where the blank is indexed half a pitch for each half revolution of the cutter and each side surface of the clutch lies in the cutter plane during the cutting of that side surface.

The same procedure, as has been describedfor cutting the sides of the teeth of the load releasing clutch member 248, may be applied in cutting a chamfer at the tops of the teeth of an adjustable clutch member. Such a member may have side tooth surfaces which are planes parallel to the clutch axis, like the clutch members shown in Figs. 12 to 14 inclusive. A clutch of this type is shown in Fig. 34. The members of this clutch are denoted at 2 and 2", respectively. Each clutch member has teeth 292 whose opposite sides 2" and 284 are planes and parallel to the clutch axis, and each clutch member ha the upper ends of its teeth chamfered to form helicoidal surfaces 2" varying lead. One side 2 of the a tooth space and the chamfered portion!" at the opposite side of the tooth space may be cut simultaneously with one group of the blades of a cutter such as shown in Figs. 15,16 and 28 and after the work has been indexed half a pitch, the opposite side 283 of the tooth space and the chamfered portion 2" may be cut simultaneously by the other group of blades of the cutter. Since the cutter has no lengthwise feed along the tooth space, the chamfered portions 2" and 286 of the 5 tooth surfaces are surfaces of revolution approximating helicoids of v ing lead, and the plane sides 2|! and 284 of course, also surfaces of revolution.

The chamfer may, of course, be applied in a separate operation. In this case constant tooth,

depth may be attained.

In a further modification of the present invention, load-releasing clutches having helical tooth surfaces of constant lead may be produced. Such as clutches may be provided with straight radial teeth, which taper in width and height from end to end as illustrated in Figs. 35 and 36. Here a clutch member 29l is shown which has radial teeth 292 whose sides are helical surfaces of constant lead. In any plane 293 perpendicular to the the tooth spaces are, of

17* tion of the clutch axis I. ate constant rate with a constant ratio between the rotary and translatory movements. All points-in the line "I or 2 will describe, therefore helicesof the same lead which appear as the profile curves'of the clutch. 'The profile curves are practically straight,

but have inclinations or pressure angles which vary along the length of the teeth." The pressure angles or inclinationincrease with increasein dis- I tance from the clutch axis.

I have found that-such clutch'members-can-be produced with disc type cutters havingcutting edges of convex profile. A cutterof the required type is shown diagrammatically in section at 3".

in Fig. 37. This cutter has blades Illl whose opposite side cutting edges are of convex shape; be

ing curved along circular arcs 302 or along any other suitable curves. Corresponding side cutting edges of successive blades of this cutter havevarying inclinations to produce the" required variation in pressure angle along the length of the clutch teeth from one end Both sides of a tooth space are simultaneously cut in a'feed motion lengthwise of the tooth space.

Another way of cutting a clutch member of the described type is illustrated diagrammatically in Figs. 38 to 42 inclusive. Here one side'of a tooth space of the clutch is cut in a half a revolution of the cutter and the opposite side of the tooth space is cut in the remaining half revolution.

A cutter of the general type shown inFig's.

and 16 is employed. This cutter has the cutting blades of each group of its blades so constructed that the corresponding sides of successive blades have varying inclination to the axis of the cutter In the cutting of a tooth space ofthe cutter, the cutter is fed in the direction of the pitch plane illl of the clutch member ill so that the axis of the cutter will move from position) to position 3H. A mean position of the cutter axis is denoted at 3H2", ,surface ofthe cutter for this mean position is denoted as shown in dottedlines atill. In the cutting of one side surface 3 of a tooth' space. the cutter will move along a line 3lIradial of the clutch axis 3l6, and in the cutting ofthe opposite side 3|! of the tooth space, the cutter will move along a radial line 3l8; The work is indexed-half a pitch for each half revolution-of thecutter when a gap in thecutter is abreast of the work.

Figs. 40"to 42 inclusive show the shapes of the blades used for cutting the outer end, center'and the inner end, respectively, of a tooth surface at one side of atooth space. The opposite side of the tooth space is cut in an exactly symmetrical manner. The profiles of the cutting blades are circular arcs fill-having a radius 32L;

For cutting at the outer end -of the clutch tooth, the center of the circular arc will be at 322 so that the blade profile 323 will have greatest inclination to a plane 324 containing the clutch axis. The center of the cutting edge 32' of the blade 326for cutting at the center of the tooth length is at 322' displaced from position 322. The blade 321, which cuts at the inner end of thetooth space, has the centerof curvature of its side cutting edge 12! still further displaced to;

a position 322" so that the inclination of the profile of the tooth space to the plane 324 will be still further reduced. Thus while the cutting edges 328 and 328 have the same radius of" curvature Ml as the cutting edge 323, their inclinations;

progressively reduced so as to out, as" desired, a tooth surface having side profiles that progressively decrease in inclination from one end to the 75 and the position of the'tipthereof to the other.

lei.

tomember' m hastooth spaces width from end to end.

' have both sidesof its 65 female cutters are required. Thestructure .70. which cuts midway the when media a tooth space-has been out.

the cutter is rapidlyreturned tov starting position and the clutch is indexed through half apitch.

Then the cutter isiagain fed across the face .of the blank to cut the opposite side .of the tooth space. Then the cutter is again returned to starting position while the work is being indexed through half the pitch. There are therefore two identical feed strokes and two'indexes per cutter revolution. 1

' Figs. 43 to-45 inclusive illustrate dia rammatically a modified form of cutter'which will'produce a still better approximation of the desired helical tooth shape Here three blades "I, I and 332 are shown which are adapted to cut, respectively, at theouter end, the center,- and the inner end of one side of a tooth space. The cutting-profile in the case of these blades is no longer reduced withreduced inclination of, the sides of theclutch teeth. The radius oicurvature 338' of the side-cutting edge I35 of theblade m, which cuts at thelarge endof the gear tooth, is greater thanthe radius of curvature 331 of the side-cutting edge 338 of the blade "I whichcuts at the center of the gear tooth, and this in turn is larger than the radius of. curvature 338 of theside cutting edge 3" of theblade "twhich cuts at the inner end :of the tooth space. 5'

A satisfactory curve of this character isan involuteoi a circle whosecenter hat "2 in Fig. 43. Diflerent positions of the involute curveare obtainedby moving the curve through a point 343 without turning it. Positions of the center of the circle 34! are'thenobtained. It is to be noted that the line "8 connecting the center as: with the'starting point fl'I-of the involute has a bodily displacement so that the lines 342-441, 342' -341 and 2"4" are all paral- The curve "334 also'has a bodily translation so that the center 2 describes a curve flliFig. 44) which is identical with the, curve ill.

Figs. 46 to 54 show a modified form of clutch.

Here one clutch 352 of uniform width from end to end; and teeth "3 which taper in width from end to end, while the other clutch member "I has teeth "l ef uniform width from end to end and tooth spaces 355 which taper in Preferably the teeth and tooth s 'aaces of both members are'made of uniform depth from end to end. The clutch member till readily lends itself-to production in an operation wherelboth sides ofa toothspace arecut and method of cutting same.

teeth cut simultaneously. For producing the two members 350 and ill of the clutch, in operations where two tooth sides are-'to be out simultaneously, a pair of male and of the male cutter for cutting the clutch member 350 is illustrated diagrammatically inFigs. 49 to 51 inclusive. 3" denotes a blade which is to cut at the large end of a tooth space length of the tooth space, and "I is the blade which cuts at the innerend of. the tooth space. It is to be noted that the inclinationof the corresponding side cutting edges 808,384 and 365 of the blades to-the-mean cuttingplane It decreases from the blade I80,

course,

342, 342' and 34 2" 352. i "I is a-blade which is adapted to cut at the outer-end of the tooth space, to the blade "I which cuts at the inner end of the tooth space, and that, similarly, the inclination of the opposite side cutting edges "1,1", and "I decreases from the blade, which is adapted to cut at theouter end of the tooth space, to the blade which is adapted tocut at the inner end of the space.

The cutter for producing the clutch, member III has its cutting blades arranged in pairs to straddle a tooth of the clutch member and cut opposite sides of the tooth simultaneously. I'll denotes the blade which is adapted to cut at the outer end of the teeth, III the blade which is adapted to cut midway ofthe tooth length, and 31! the blade which is adapted to cut at the inner end of the teeth. The opposite side-cutting edges of the blade "I are denoted at 813 and 8'", respectively. The opposite side-cutting edges of the blade 3-! l are denoted at I'll and I'll, respectively, while the opposite side-cutting edges of the blade 812 are denoted at land 3'", respectively. It will be noted that the inclination of the corresponding side-cutting edges of the blades to the mean cutting plane III of the cutter decreases progressively from the blade which cutsat the outer end of the teeth to the blade which cuts at the inner end of the teeth. Preferably; at the common pitch line I of the clutch members, the inclinations oi the side cutting edges 3" and 301, which cut at the outer ends of the tooth spaces of the clutch member fll,.equals the inclination of the edges 3'" and 311 of the blade ill which cuts at the outer ends of the engaging sides of the teeth of the mating clutch member 3". Likewise, cutting edges "1, "I, III have, respectlvely, the same inclination at the pitch line as the cutting edges 3'", I'll and 81!, respectively, which cut corresponding points along the opposite matingtooth sides. 7 r

The opposite side cutting edges of both cutters are of conv'exprofile shape. The profiles may be circular arcs, or they may be lines of varying curvature whose curvature radius increases from the bottom of the cutting profile to the outside thereof.

The side surfaces to be cut on the clutch members are hellcoids of opposite hand and of constant lead whose generatrices 392, 383 and "4 and I" inany plane perpendicular to the clutch axis "I are straight lines extending longitudinally of the teeth but oifset from the clutch axis.

For cutting either member of the pair, the required cutter is rotated on its axis "1 or I" while a straight line feed movement is produced between the cutter and the work across the face of the work in time with the cutter rotation.

Depthwise feed may be employed to move the cutter into full depth, but when full depth position is reached, the lengthwise feed movement will preferably be in the direction of the pitch line III.

In Fig. 47, the position, at a mean point in the longitudinal feed movement, of the tip cutting surface of the cutter, which is used for cutting the clutch member "I, is denoted at I", while 3" denotes the position of the axis of the cutter for this mean position. As either cutter is fed along the pitch line of the clutch blank, the varying inclination of the cutting profiles continuously matches the known varying inclination of the helical tooth sides which it is desired to approximate. Contact between the cutting edges of the cutter and thetooth surface being pro- 7 duced on the work is along a line extending diagonally across :the tooth surfaces,- ordinarily more in a longitudinal direction than inthe direction of the tooth profile. This line can be determined mathematically by the requirement that the tooth normals at all points in the line must pass through the instantaneous axis of rela tive motion. The-instantaneous axis depends on the rate of feed as compared with the cutter rotation and is parallel to and not far from the cutter axis.

On account of the inclination of the line of instantaneous contact, the cutting profiles and the tooth profiles do not fully match one another in an axial plane of the cutter, but they do contact with one another at the pitch point. While the tooth profile of thehelicoid is substantially straight, the cutting profile must be convex. Its curvature can be determined mathematically with the directions given. It can also be determined experimentally by first making the helical clutch surface of constant lead, for instance by the method illustrated in Fig. 23, and thenusing that surface to produce therequired cutting edge on a dummy blade of soft material which is rotated and fed across the face of the blank at the same rate as the cutter which is to be used to cut the clutch members.

While several diiferent embodiments of the invention have been described, it will be understood that it is capable of further modification, and this application is intended to cover any adaptations, uses, or modification of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the gear art and as may be applied to the essential features hereinbefore set forth and as fall within the scope of theinvention or the limits of the appended claims.

Havingthus described claim is:

l. The method of cutting the tooth surfaces of a face clutchmember which comprises employing a rotary disc cutter having a plurality of cutting blades arranged in two groups around its periphery with a gap between the last and first blades of each group, the two groups containing, blades which are shaped to cut opposite sides of the tooth spaces of the work, rotating said cutter in engagement with the work and effecting a relative feed movement between the cutter and the work in time with the cutter rotation while each group of blades is in operation, and indexing the work half a pitch each time after a group of blades has taken its cut.

2. The method of cutting the tooth surfaces of a face clutch member which comprises employing a rotary disc cutter having a plurality of cutting blades arranged in'two groups around its periphery with a gap between the last and first blades of each group. each group comprising a plurality of roughing blades followed by one or more flnishing'blades, the finishing blades of the two groups being shaped to cut opposite side tooth surfaces of the work, respectively, rotating said cutte in engagement with the work, efi'ecting. a-relative feed movement between the cutter and work intime with the cutter rotation while each group of blades is in operation, withdrawing the cutter from engagement with the work after each group of blades has taken its cut, and indexing the work half a pitch on'each withdrawal while a gap in the cutter is abreast of the work.

3. The method of cutting the tooth surfaces of my invention, what I,

a face a rotary disc cutter having a plurality of. cuttin blades arranged in two,groups' aroundits periphery with a gap between the last and first blades or each group, each group having a plu clutch member which co prises empl yi l rality of roughing blades followed by one or more dexing the work half a pitch d r a h Withdrawal. a. 4. The method of cutting aface clutch memberv which comprises employing a rotary disc cutter having a plurality of cuttingtblades arranged in two groups around itsperiphery with a gap between the last and first blades of each group. the blades of the two groups being shaped to cut opposite side tooth surfaces of the work, respectively, and effecting a relative lengthwise reed movement between the cutter and -work in time with the cutter rotation in one direction while each group of blades is cutting and in the opposite direction while each gapeis abreast of the work, and indexing the work half a' pitcheach time a gap in the cutter is abreast of the work.

5. The method of cutting the tooth surfaces of a face clutch member which comprises employing a rotary disc cutter that has a plurality of peripherally arrangedcutting blades which are dispwed in two groups with a gap between the last blade of each groupand the first blade of the other group, the blades of each group being of progressively varying point-width, and rotating said cutter in engagement with the work while producing a relative lengthwise feed movement between the cutter and work in timewith the rotation or the cutter and in a direction radial 0! the clutch axis so that different blades oi the cutter cut at diflerent points along the length of a tooth surface during a revolution of the cutter, and indexing the time a gap in the cutter is abreast of the work.

6. The method of cutting the tooth surtacesot; a face clutch member which comprises employing a rotary disc cutter'that has a plurality of peripherally arranged'cutting blades disposed'in two groups with a gap between the last blade oi each group and the first blade. of the other group, the blades of each group being or progressively varying point-width, and rotating said, cutter in engagement with the work while pro-. ducing a simultaneous relative depthwise and lengthwise feed movement between the cutter and work in time with the cutter rotation until the cutter reaches full depth position, and then eiiecting'relative lengthwise feed movement between the cutter and the work also in time with the cutter'rotation so that different blades of .the cutter cut at progressively different points along the length 01 a tooth'surface of the work from one end thereof to the other as the cutter rotates in engagementwith work halt a pitch each time a. gapin, the cutter is abreast of the work. a

22 having sides group. the blades perpendicular to the cutter axis and tip cutting edges concentric ,0! said axis, each group of blades having a plurality or roughing blades followed by one or more finisbingblades. the finishing blades oi the two groups being shaped to cut opposite tooth sides of the work, respectively, engagement with the work, feeding the cutter depthwise into the work while roughing blades of each group are cutting until full depth position is reached, allowing the cutterfto' remain at full depth whilethe finishing blades of each roup are cutting, and withdrawing the cutter from engagement withthe work while each gap in the cutter is abreast of the work, and index-. ing the work withdrawal. g

.8. The method of producing an approximately helicoidal tooth surface of varying'leadon a side or a tooth or a toothed ,iace clutch member, which comprises employing a rotary disc cutter that has a plurality of cutting blades of curvedprofile width, and that has the centers-oi curvature of corresponding side profiles of successive blades progressively displaced from one another. positioning said cutter so that its axis is disposed at a greater radial distance -from the clutch axis than the meanradius of, the clutch, rotating said cutter in'engagement with the work while effectinga relative depthwise teed motion between thecutter and the work in time with the cutter rotation while maintaining the cutter axis at said greater radial distance, and periodically indexing the work. I

9. a The method of producing a face clutch member which comprises employing a rotary disc cutter having a plurality .of cutting blades arrangedtin two groups around its periphery with agap between the last and first blades of each group,'the blades of one group being adapted to I cut one side ofa tooth space ot the work and work. halt a pitch each the work, and indexing the '7. The method of cutting tooth surfaces oia face clutch member which comprises employing a rotary disc cutter that has a plurality of blades arranged in two groups around its axis-with a gap between the last and first blades or each.

being adapted the tooth space opposite to those out and chamfered, respectively, by the first group of blades,

chamfer thev opposite side of said tooth space at the top thereof, and the blades of the other, group to cut and chamfer the sides of and rotating said cutter inengagement with the work, producing a relative feed movement between the'cutter and'work while each group of blades is cutting, withdrawing the cutter from engagementwith the the cutter is abreast of the work, and indexing is vgrk through half a pitch on each with- 10. A. rotary disc cutter having a plurality of I radially disposed cutting blades arranged in two groups around the periphery of the cutter with a gap between thelast blade or each group and the first blade oithe other group, the blades of the two groups lying, respectively, at opposite sides of a plane of rotation perpendicular tothe axis oi. the cutter.

v 11. A rotary disc cutterhaving a plurality of radially disposed cutting blades arranged in two groups around the periphery of the cutter with a gap between the last blade of each group and the first blade of the other group, each group of blades comprising a plurality of roughing blades and one 'or morefinishing blades, the two groups of blades lying, respectively, at opposite sides of a plane of rotation perpendicular to the axis of the cutter, and the finishing blades or the two groups having opposite side-cutting edges-lyin in said plane.

rotating said cutter in throughhali. a pitch during each shape and progressively varying pointworkeach time a gap in 12. A rotary disc cutter having a plurality of radially disposed cutting blades arranged in two groups around the periphery of the cutter with a gap between the last blade of each group and the first blade of t e other,group'..the blades ofv one group having cutting edges for cuttin one side and chami'ering the opposite side of a tooth space. and the blades or the other group having cutting edges for cutting and 'chamiering, respectively, the sides or the. tooth space opposite to thou cut and chamiered by the first group of blades.

13. A rotary disc cutter having a plurality of radially disposed cutting blades arranged intwo groups around the periphery of the cutter with a gap between the last blade of each group and the first blade of the other group, the blades of one group having cutting edges for cutting one side and 'chamfering the opposite side oi a tooth space, and the blades of the other group having cutting edges for cutting and chamfering,- respectively, the sides or the tooth space opposite those out and chamiered, respectively, by the first group of blades. the cutting edges for cutting a given side of the tooth space having the same inclination to the axis or the cutter, and the cutting edges for chami'ering a given side or the tooth space having progressively varying inclination to the axis of the cutter. Y

14. A rotary disc cutter having a plurality oi radially disposed cutting blades arranged-in two groups with a gap between the last blade or each roup and the first blade of the other group; the blades 01' each group having straight side-cutting edges or constant inclination with respect to a plane 01' rotation perpendicular to the axis of the cutter and having tip cutting edges oi. varying point-widtharranged at a uniform distance from the cutter axis, the side-cutting edges at the same side of the blades of each group having varying positions along said axis, and the blades of the two groups lying, respectively, at opposite sides 01' a plane of lar to the axis of the cutter.

15. A rotary disc cutter having a plurality of radially disposed cutting blades arranged in two groups around its periphery with a gap between the last blade 01' each group and the first blade oi the other group, the blades of each group having curved side cuttingedges, successive side cutting edges at the same side 01' the blades oi each group having progressively varying inclination to a plane of rotation perpendicular to the cutter axis, the curvature of successive side cutting edges oi each group increasing with decreasing inclination of the side-cutting edges to said plane.

16. The method of cutting a toothed i'ace clutch member which comprises employing a rotary disc cutter having a plurality of cutting blades arranged in two groups around its periphery with a gap between the last blade or each group and the first blade or the other group, each group having a plurality of roughing blades followed by one or more finishing blades, the blades 01' the two groups being sharpened to cut opposite tooth sides, respectively, the finish cutting edges or the finishing blades oi the two groups being oi straight profile shape and lying ina common plane perpendicular to the axis or the cutter and the roughing blades of the two groups being of progressively varying point width and being ofiset at oppositesides of said plane, respectively, rotating said cutter in engagement with the work while efiecting a relative depthwise iced movement between the cutter and work in rotation perpendicutime with the cutter rotation to cut one side oi a tooth space of the work, then withdrawing the cutter from engagement with the work and indexing the workthrough hall a pitch while one 6 of the gaps in the cutter is abreast of the work, and repeating the cycle of feed, withdrawal and indexing until the work is completed.

17. The method of cutting a toothed face clutch member which comprises employing a rotary disc cutter having a plurality of cutting blades arranged in two groups around its periphery with a gap between the last blade of each group and the first blade of the other group, each group having a plurality oi roughing blades followed by one or more finishing blades, the blades or the two groups being sharpened to cut opposite tooth sides, respectively, the finishing blades of the two groups being of curved profile I shape and the roughing blades of each roup be- 20 ing of progressively varying point width, positioning said cutter so that its axis is disposed at a greater distance from the clutch axis than the mean radius or the clutch, and rotating said cutter in engagement with the work while efiecting a relative depthwise i'eed movement between the cutter and work in time with the cutter rotation to cut one side 0! a tooth space of the work, then withdrawing the cutter i'rom engagement with the work and indexing the work half a pitch while one of the gaps in the cutter is abreast oi the work, and repeating the cycle oi feed, withdrawal and indexing until the work is completed.

18. Themethod oi cutting a toothed face clutch memberwhich comprises employing a rotary disc cutterhaving a plurality 0! cutting blades arranged in two groups around its periphery with a gap between the last blade or each group and the first blade of the'other group, each group having a plurality of blades of progressively varying point width, and rotating said cutter in engagement with the work while effecting arelatlve lengthwise feed movement between the cutter and work in time with the cutter rotation, then withdrawing the cutter from engagement with 45 the work and indexing the work half a pitch while one of the gaps in the cutter is abreast 01' the work; and repeating the cycle of feed, withdrawal, and indexing until the work is completed. 19. The method of producing a toothed face so clutch member which comprises employing s rotary disc cutter having a plurality oi cutting blades arranged in two groups around its periphery with a gap between the last blade of each group and the first blade of the other, corress spondnig side cutting edges of successive blades of each group having progressively varying inclination to a plane of rotation perpendicular to the axis of the cutter. and rotating the cutter in engagement with the work while efi'ecting a go relative teed movement between the cutter and work longitudinally oi a tooth oi the work in time with the cutter rotation, and periodically withdrawing the clltter from engagement with the work and indexing the work halt a pitch during withdrawal and while a gap in the cutter is abreast of the work. 7

20. The method of producing a toothed face member which comprises employing a roclutch tary disc cutter having a plurality of cutting 70 blades arranged in two groups around its periphcry with a gap between the last blade of each group and the first blade of the other group, the

blades or each group being oi progressively vary: ing point width and having straight side cutting 76 edges at one side for cutting one side of a tooth 

